Assuming the device does in fact have an IR blaster (not all phone / tablet models do despite having similar sounding names), it could be a few things.
- Be sure that you are aiming the phone or tablet's IR blaster directly towards the bottom of the TV when controlling volume, mute or power on the TV. If using IR to control the DirecTV receiver, be sure you are aiming it towards the DirecTV receiver when controlling DirecTV functions.
This problem is actually quite common, especially when unfamiliar with how well (or not) the IR works on these devices. Unfortunately they are not nearly as powerful as the real remotes often are. With the real remote you may get away with aiming it several feet away from the TV where as the phone may require much more precise aim.
- It's also possible that none of the IR presets in the app work with your particular TV or AVR model. If your brand is not listed or none of the presets work, please send me an email using the 'Report' button in the Volume plugin. Be sure to mention your brand (and model if known) and I can probably get working codes for you. You should definitely check your aim though as mentioned above. While it could be an IR code problem, if it is an aiming problem then it could very well be a waste of time to ask for different IR codes.
- This may be fixed by now, but if you are using a Samsung Galaxy device, please be sure that "Power Saving Mode" is turned off. While the IR blaster appears to still work (when viewed through a digital camera), it apparently does not send the signal correctly when Power Saving Mode is turned on. This is/was a known issue with the Galaxy Tab 2 and possibly other Galaxy models.
Another thing to try is to see if you can get the remote app that came with the phone or tablet to work. If the "stock" app does not work, then you may want to seek help with that before trying to get the DirecTV Remote+ or Volume Plugin to work. All phones and tablets with built-in IR blasters come with some kind of remote control app. If you can't find one on your phone, try searching Google for more information on how to use the IR / remote on your specific phone or tablet.